The possible role of the age of the human host in determining the localization of hydatid cysts.

Cystic hydatid disease or cystic echinococcosis (CE) is a cyclozoonotic infection distributed world-wide. The morbidity attributable to the infection depends on the size of the cyst(s) and the organ(s) involved. The cysts are most commonly found in the liver and lungs but certain locations have been reported to be more prevalent in children and/or young adults than in older subjects. In order to identify the relationship, if any, between the age of the patient and the site of involvement, the age and cyst distribution of 92 cases of CE were analysed. Lung, brain, spinal and orbital hydatid cysts were more commonly seen in younger patients whereas other sites were preferentially involved in older patients. The factors that determine the final localization of the cysts are discussed. It is concluded that age somehow alters the host-parasite relationship and thus affects the organ distribution of the cysts.